Efforts to improve upon the performance of natural mineral oil-based lubricants by the synthesis of oligomeric hydrocarbon fluids have been the subject of important research and development in the petroleum industry for at least fifty years. These efforts have led to the relatively recent market introduction of a number of synthetic lubricants. In terms of lubricant property improvement, the thrust of the industrial research efforts involving synthetic lubricants have been towards fluids exhibiting useful viscosities over a wide temperature range, i.e., improved viscosity index (VI), while also showing lubricities, thermal and oxidative stabilities and pour points equal to or better than those for mineral oil.
Poly-alphaolefins (PAOs) comprise a class of hydrocarbons manufactured by the catalytic oligomerization (polymerization to low-molecular-weight products) of linear α-olefin (LAO) monomers. These typically range from 1-octene to 1-dodecene, with 1-decene being a preferred material, although oligomeric copolymers of lower olefins such as ethylene and propylene may also be used, including copolymers of ethylene with higher olefins as described in U.S. Pat. No. 4,956,122 and the patents referred to therein. PAO products have achieved importance in the lubricating oil market. Typically there are two classes of synthetic hydrocarbon fluids (SHF) produced from linear alpha-olefins, the two classes of SHF being denoted as PAO and HVI-PAO (high viscosity index PAO's). PAO's and HVI-PAO's of different viscosity grades are typically produced using promoted BF3 or AlCl3 catalysts.
Synthetic PAOs have found wide acceptability and commercial success in the lubricant field for their superiority to mineral based lubricants. In terms of lubricant property improvement, industrial research efforts on synthetic lubricants have led to PAO fluids exhibiting useful viscosities over a wide range of temperature, i.e., improved viscosity index, while also showing lubricity, thermal and oxidative stability and pour point equal to or better than mineral oil. These relatively new synthetic lubricants lower mechanical friction, enhancing mechanical efficiency over the full spectrum of mechanical loads and do so over a wider range of operating conditions than mineral oil lubricants.
One benefit of premium lubricants is the potential for extended life, reducing the change-out interval. Extended lubricant life is one feature that offsets the higher initial fill cost for premium lubricants. In order to achieve an extended lubricant life, premium lubricants must demonstrate a more stable viscosity in service. Using higher quality base stocks and advanced additive systems, these lubricants counter the effects of thermal, oxidative and hydrolytic attack.
The use of single-site metallocene catalysts in the oligomerization of various alphaolefin feeds is known per se, such as in WO2007/011832, WO2007/011459, and WO2007/011973. To date however, PAOs made with metallocenes have yet to find wide applicability in the marketplace, particularly the lubricant marketplace, due to inefficient process, cost and property deficits. The instant invention address such and other needs by providing metallocene catalyst produced PAOs manufactured by improved processes and equipment.